This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-066052, filed Mar. 10, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to an automatic travel control apparatus for a vehicle for making a vehicle automatically or autonomously travel along a given path and, more particularly, to an automatic travel control apparatus for a vehicle, which can assure very high traceability and stability.
Conventionally, in the field of travel control of a vehicle, as a technique that pertains to lane change and obstacle avoidance action, a scheme for computing a steering angle by feedforward control on the basis of the goal angle, the distance to an obstacle, or the like is known, as described in, e.g., xe2x80x9cJpn. Pat. Appln. KOKAI Publication No. 7-160995xe2x80x9d.
In a method of computing a steering angle by feedback control, the steering angle is computed using the vehicle declination and side displacement amount as inputs.
FIG. 1 is a block diagram showing an example of the method of computing the steering angle by a feedback computation.
That is, as shown in FIG. 1, the vehicle declination and side displacement amount are respectively multiplied by gains, and these products are added to obtain a steering angle command.
On the other hand, as a technique that pertains to path track automatic travel control, a method of embedding magnetic markers in the road surface on which a vehicle travels, and tracking the magnetic markers is known, as described in xe2x80x9cJpn. Pat. Appln. KOKAI Publication No. 10-105892xe2x80x9d or xe2x80x9cJpn. Pat. Appln. KOKAI Publication No. 10-105232xe2x80x9d. In this method, a computation is made based on the distance from the path or the like.
However, in the method described in xe2x80x9cJpn. Pat. Appln. KOKAI Publication No. 7-160995xe2x80x9d, the feedforward computation stands only under the condition of constant velocity, and a steering angle command is output by time management.
In this case, when a velocity corresponding to the command is not output, a future vehicle body state is indeterminable, and such control is not appropriate.
As for the steering angle command obtained by the feedback computation using the side displacement amount and vehicle declination, if the gains are constant, since two inputs are used, the output controlled variable may diverge depending on the magnitudes of the inputs, and stable control is hard to attain.
On the other hand, in the method using the magnetic markers described in xe2x80x9cJpn. Pat. Appln. KOKAI Publication No. 10-105892xe2x80x9d or xe2x80x9cJpn. Pat. Appln. KOKAI Publication No. 10-105232xe2x80x9d, magnetic markers must be embedded in the road surface.
Also, when a vehicle deviates from the magnetic markers, it becomes impossible to continue control.
Furthermore, an accurate vehicle position orientation angle cannot be detected based on the magnetic markers.
It is an object of the present invention to provide an automatic travel control apparatus for a vehicle, which can realize autopilot of a vehicle with very high traceability and stability.
In order to achieve the above object, according to the present invention, an automatic travel control apparatus for controlling a vehicle which mounts a controllable steering unit and drive unit to make it automatically travel according to a given path, comprises storage means for holding data which pertain to specifications and data of the vehicle, path information obtaining means for obtaining path information of a path the vehicle is to travel, which consists of position, orientation, and velocity data, and is given by point information, path computing means for computing a path equation including equations of continuous straight lines and arcs and a velocity pattern, which pertain to automatic travel, on the basis of the data held by the storage means and the path information obtained by the path information obtaining means, absolute position-orientation angle detection means for detecting an absolute position and absolute orientation angle of the vehicle, steering control means for controlling the steering unit to track the path equation on the basis of the path equation computed by the path computing means, and the absolute position and absolute orientation angle of the vehicle detected by the absolute position-orientation angle detection means, and a drive control unit for controlling the drive unit to track the velocity pattern on the basis of the velocity pattern computed by the path computing means and a velocity of the vehicle.
In the automatic travel control apparatus for a vehicle according to the present invention, since path or route information along which the vehicle is to travel is given in advance to instruct the coordinates of the path the vehicle is to travel, and the vehicle orientation angle at that position, the feedback control of steering (direction) and drive (velocity) of the vehicle is made using the detected absolute position and absolute orientation angle of the vehicle, thus realizing automatic travel of a vehicle with high traceability.
In this way, automatic steering and velocity control is made, and automatic travel of a vehicle with very high traceability and stability can be realized.
Furthermore, the path information obtaining means comprises a management center for managing travel of the vehicle, and supplying path information of the path the vehicle is to travel, means for making two-way communications between the management center and the vehicle, and means for receiving the path information of the path the vehicle is to travel, which is supplied from the management center, and when the vehicle transmits information such as a current vehicle position, goal, and the like to the management center, the management center transmits path information to the goal to the vehicle.
Therefore, in the automatic travel control apparatus for a vehicle according to the present invention, since the vehicle designates/transmits a goal, path information such as coordinate positions where the path changes (right and left traverses, lane changes, and the like) in the path to the goal, the velocity at that coordinate position, the radius of gyration upon traverse, and the like is sent from the management center. Then, a continuous path equation is computed based on such path information. The vehicle can transmit information such as the current vehicle position, goal, and the like to the management center.
According to the present invention, the path information obtaining means comprises means for designating a goal to which the vehicle is to travel, means for holding map information to the goal, and means for computing and selecting a path to the designated goal on the basis of the held map information, and when a goal of the vehicle is designated, path information to the goal is computed.
Therefore, according to the present invention, when the goal is designated, path information such as a path to the goal, the coordinate positions where the path changes (right and left traverses, lane changes, and the like), the velocity at that coordinate position, the radius of gyration upon traverse, and the like is computed, and the path equation is computed based on the computed information.
Furthermore, according to the present invention, the steering control means comprises means for computing a positional deflection as a deflection between the path equation computed by the path computing means, and a current absolute position of the vehicle, means for computing an orientation angle deflection as a deflection between a goal orientation angle of the vehicle in the path equation computed by the path computing means, and a current absolute orientation angle of the vehicle, means for computing a steering angle command of the vehicle to make the positional deflection and orientation angle deflection close to zero, and means for controlling a steering angle of the vehicle in response to the steering angle command of the vehicle.
Therefore, according to the present invention, the current positional deflection and orientation angle deflection of the vehicle are accurately computed, and a steering angle command of the vehicle is computed to make these deflections closer to zero, thus controlling the steering angle of the vehicle.
Moreover, the apparatus further comprises means for transmitting travel path information including obstacle information such as accident information, roadwork information, and the like, which are associated with a leading vehicle, to the management center as history information, and means for updating path information of the path the vehicle is to travel, which is to be supplied to a trailing vehicle, on the basis of the transmitted history information.
Therefore, according to the present invention, since travel path information including obstacle information that pertains to a leading vehicle is transmitted to the management center as history information, the management center updates information of the path the vehicle is to travel, which is supplied to a trailing vehicle to reflect obstacles upon travel of the leading vehicle in travel control of the trailing vehicle, thus realizing automatic travel of a vehicle with higher reliability, which considers traffic accidents, roadwork, and the like.
According to the present invention, a feedback computation upon controlling the steering unit to track the path equation or upon controlling the drive device to track the velocity pattern uses fuzzy reasoning.
Therefore, when fuzzy reasoning is used in the feedback computation upon executing steering control and drive control, since gains are variable, the vehicle position and orientation angle can be controlled without any interference, thus realizing more stable travel control.
As described above, according to the automatic travel control apparatus for a vehicle of the present invention, the absolute position and absolute orientation angle of the vehicle are obtained, information of a path the vehicle is to travel is acquired, a continuous path equation and velocity pattern, which pertain to automatic travel, are computed on the basis of the path information, and direction control by the steering unit and velocity control by the drive unit are made to track these path equation and velocity pattern. Therefore, automatic steering and drive control is achieved, and automatic travel of a vehicle with very high traceability and stability can be realized.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.